Heat dissipation from an integrated circuit (IC) chip or die during operation is typically an important issue, especially as the density of IC devices on a chip continues to increase. Also, many devices now have combinations of high-power transistors and low-power transistors formed on a same chip. Such high-power transistors tend to produce more heat than low-power transistors. Further, more system-on-chip configurations are being used. Thus, there are often a wide variety of IC devices on a same chip. Some of the IC devices can handle and/or put out much more heat than nearby or neighboring devices on the same chip. Hence, the reliability and effectiveness of heat dissipation for a packaged IC chip may greatly affect the reliability and/or performance of an IC chip during operation.
Many conventional die package assemblies have an exposed die pad surface. Typically an IC chip is soldered, bonded, or adhered to a die pad to improve heat transfer from the die via the die pad. In the case of soldering the IC chip to the leadframe, the chip typically has a solderable backside metallization for attachment to the die pad using a high melting temperature solder which is typically lead-based. An exposed die pad is often attached to a heat sink member such as but not limited to a metal feature on a printed circuit board (PCB) to provide a primary heat transfer path from the chip to the heat sink via the die pad. However, in the case of soldering the chip to the leadframe where a high lead alloy is used, it would be desirable to eliminate lead-based alloys from packages. Also, there is a continued need for improved IC chip package designs that provide efficient heat transfer from the chip during operation.